Charge transport in molecular and extended systems is discussed with special reference to the mixing of covalent and ionic states and the evolution of this mixing with time. The formalism allows the electron to acquire an extra phase when it moves from one site to the next so that a hopping limit can be reached where the electron transfers with a random phase. The equations of motion are solved for both quantum mechanical and classical dynamics. An appendix discusses a classical representation of orbital occupancies in a manner consistent with the Pauli exclusion principle.